The present invention relates to a vaned hydraulic system such as a vane pump or a vane motor, more specifically a vaned hydraulic system the longitudinal length of which can be reduced.
The vaned hydraulic system such as a vane pump can be used as a hydraulic pump for an automatic transmission of a vehicle.
One example of such conventional vane pumps is shown in FIGS. 1 and 2, wherein a hydraulic vane pump for a automatic transmission is generally indicated by reference numeral 1. The vane second pump 1 has a housing 4 comprising a first pump cover 2 and a pump cover 3. The pump cover 2 is integrally formed with a hollow fixed shaft 5 which is loosely inserted into a longitudinal hole 6 in the pump cover such that the fixed shaft 5 is coaxial with the longitudinal hole 6. Located within the housing 4 are a stationary cam ring 7 of a substantially cylindrical configuration, a substantially cylindrical rotor 8 rotatably disposed within the cam ring 7 in a coaxial relationship with the fixed shaft 5 and in an eccentric relationship with the cam ring 7, a plurality of vanes each slidably disposed in a radial groove within the rotor 8 and adapted to project radially outwardly from the outer circumferential surface of the rotor to abut slidably at its tip against the inner circumferential surface of the cam ring 7, and a pair of vane rings 10 and 11 disposed at the opposite sides of the rotor 8 concentrically with respect to the cam ring 7 within the rotor 8 to guide the vanes 9 to abut slidably at the tips thereof against the inner surface of the cam ring 7. The vane rings 10 and 11 are disposed rotatably with respect to the rotor 8 within circular recesses 12 and 13 respectively. The circular recesses 12 and 13 are defined by portions depressed or less in thickness (longitudinal length) at the opposite sides (the right and left sides as viewed in FIG. 1) of the rotor 8. A hollow pump driving shaft 14 as a power transmission shaft is inserted at one end thereof into the housing 4 from the outside of the housing 4 through the longitudinal hole 6 provided within the pump cover 3. The pump driving shaft 14 is also inserted coaxially into the central hole 15 at the center of the rotor 8 and connected with the rotor 8 so as to rotate integrally therewith. The other end (not shown) of the pump driving shaft is connected with a crank shaft of an engine (not shown) through a pump impeller of a torque converter (not shown). A centering member 16 is disposed within the rotor 8 and adapted to be positioned between the rotor 8 and the housing 4 so as to position the rotor 8 before inserting the driving shaft 14 into the housing 4 such that the central hole 15 of the rotor 8 is arranged coaxially with the hole 6 of the housing 4 thereby smoothing insertion of the driving shaft 14 into the central hole 15. The centering member 16 has a cylindrical portion 16a and a flange portion 16b extending radially outwardly from the cylindrical portion 16a. The cylindrical portion 16a is adapted to be inserted into the hole 6 of the housing 4 whereas the flange portion 16b abuts on the circumferential wall 13a of the recess 12 of the rotor 8, whereby the rotor 8 is positioned.
As will be understood from the foregoing description, the vane rings 10 and 11 and the flange portion 16b of the centering member 16 are placed in series in the axial direction of the rotor 8 within the recesses 12 and 13 of the rotor 8. Accordingly, the thickness (axial length) t of the radially inward portion between the recesses 12 and 13 of the rotor 8 must be thinner than that T of the radially outward portion by the amount equivalent to the substantially total thickness of the two vane rings 10 and 11 and the flange portion 16b of the centering member 16.
The vane pump is constructed such that when the driving shaft 14 is rotatingly driven by the engine (not shown), the rotor 8 is rotated together with the driving shaft thereby causing the vanes to draw hydraulic fluid from a suction conduit or passage (not shown) and discharge the same to a discharge conduit or passage (not shown).
In such a prior art vane pump 1, however, the two vane rings 10 and 11 and the centering member 16 are positioned in series in the axial direction of the rotor as previously set forth, so that the thickness (axial length) t of the radially inward portion of the rotor 8 is less than the thickness T of the radially outward portion, which would reduce the mechanical strength at the radially inward portion of the rotor 8 where forces from the driving shaft 14 are directly imposed. Consequently, in the prior art vane pump 1, the thickness t of the rotor 8 at the radially inward portion thereof must be large enough to provide for reliable strength, whereas the thickness T of the rotor 8 at the radially outward portion thereof is correspondingly thicker than the thickness t by the amount equivalent to the total thickness of the vane rings 10 and 11 and the flange portion 16b of the centering member 16. This would enlarge the axial length of the rotor and therefore the whole axial length of the vane pump 1, which would in turn make the vane pump 1 heavy in weight.
Accordingly, the primary object of the present invention is to reduce the whole axial length of a rotor without decreasing the mechanical strength of the same.
Another object of the present invention is to avoid the reduction in thickness at the radially inward portion of the rotor as much as possible.
Another object of the present invention is to provide a compact and light-weighted vaned hydraulic system, thereby overcoming the problems in the prior art hydraulic system as mentioned above.